h1 {
    width: 1000px;
    height: 100px;
    text-align: center;
    background-color: gray;
    display: flex; /* 启用 Flexbox */
    justify-content: center; /* 水平居中 */
    align-items: center; /* 垂直居中 */
    margin-bottom: 0;
    border-bottom: 1px solid black;
}

a {
    text-decoration: none; /* 去除下划线 */
    color: inherit; /* 继承父元素的颜色 */
}
.body>div{
    float: left;
}
.body{
    overflow: hidden;
}

ul{
    margin: 5px 0 0 0;
    padding-left: 20px;
}

.left {
    width: 150px;
    height: 1000px;
    background-color: gray;
    padding-left: 10px;
}

.content{
    width: 670px;
    height: 1000px;
    padding-left: 10px;
}

.right{
    width: 150px;
    height: 1000px;
    background-color: gray;
    padding-left: 10px;
}

p{
    text-indent: 2em;
}